This invention relates to a process and device for spraying a liquid by means of an atomizing gas and their application in the preparation of melamine.
It is already known that a liquid can be sprayed by means of a two-phase sprayer consisting of two concentric tubes, in which liquid flows through the central tube and the gas flows through the annular channel between the inner and the outer tube. According to U.S. Pat. No. 3,377,350 the spraying of urea is preferably effected by means of sprayers in which the outflow opening of the gas is in the same plane as the outflow opening of the urea, and the outflow velocity of the gas is preferably higher than the velocity of sound. According to Netherlands Patent Application No. 6,902,755, urea is sprayed by means of sprayers in which the outflow opening of the gas is in front of the outflow opening of the urea, or in which both openings are in the same plane. According to this Patent Application a gas outflow velocity of at most 100 m/sec is used. The sprayers described above all have the drawback that their capacity is limited, because either a poor atomization occurs during spraying, a very large amount of atomizing gas is required, or a high gas velocity is needed in spraying large amounts of liquid, especially molten urea.
The present Application is directed to providing a two-phase sprayer that can also efficiently spray comparatively large amounts of liquid at low gas velocities, preferably at a velocity of at most 100 m/sec.